Air conditioner and method of controlling the same

ABSTRACT

An air conditioner having a low-pressure switch and a power supply unit. The low-pressure switch shuts off the supply of power to an indoor unit if a refrigerant pressure in a suction side of a compressor is decreased. The power supply unit supplies power to the indoor unit of the air conditioner so that a heating operation is performed using an electric heater mounted in the outdoor unit even though the low-pressure switch is turned off. The power supply unit may supply power to the indoor unit if an outdoor air temperature is equal to or lower than a preset reference temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Korean Patent Application No. 2001-75153 filed on Nov. 30, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an air conditioner and a method of controlling the same, and more particularly to an air conditioner and method of controlling the same which is capable of supplying power to an indoor unit to allow a heating operation to be performed using an electric heater even though a low-pressure switch is turned off due to a drop in refrigerant pressure.

[0004] 2. Description of the Related Art

[0005] In a conventional air conditioner, a cooling operation is performed using a refrigerant cycle while a heating operation is performed using an electric heater.

[0006] An indoor unit of the conventional air conditioner, as shown in FIG. 1, comprises: an air inlet 2 and an air outlet 4 formed on the lower and upper portions of the front of a unit body 1 to suck in and discharge indoor air, respectively; an air filter 3 positioned behind the air inlet 2 to remove impurities from the indoor air sucked through the air inlet 2 ; a wind direction adjusting vent grill 6 mounted in front of the air outlet 4 to adjust the direction of air being discharged through the air outlet 4, an indoor fan motor 7 mounted in a duct 8 to suck in the indoor air through the air inlet 2 and discharge it to indoor space, an indoor heat exchanger 5 mounted behind the air inlet 2 to cool indoor air sucked through the air inlet 2 by heat exchange, and an electric heater 9 mounted in the upper portion of the duct 8 to heat indoor air sucked through the air inlet 2 by heat exchange.

[0007] In addition, the conventional air conditioner further comprises a low-pressure switch (not shown in FIG. 1) to prevent a compressor from being damaged by a drop in refrigerant pressure.

[0008] Referring to FIG. 2, a low-pressure switch 12 is connected in series to a coil of a power relay 11 positioned between an external power source 10 and an indoor unit, and the contact of the power relay 11 is turned on or off by the operation of the low-pressure switch 12 to supply or interrupt power, respectively. For example, when the refrigerant pressure in the suction side of the compressor is higher than a reference pressure, the low-pressure switch 12 is turned on, thus supplying a driving power of +12V to the coil of the power relay 11. On the other hand, when the refrigerant pressure in the suction side of the compressor is equal to or lower than a reference pressure, the low-pressure switch 12 is turned off, thus shutting off a driving power of +12V from the coil of the power relay 11.

[0009] When the low-pressure switch 12 is kept on, an indoor unit microcomputer 13 controls an electric heater drive unit 14 so that the electric heater 9 is operated, thereby performing a heating operation.

[0010] However, in the conventional air conditioner, when the low-pressure switch mounted in the suction side of the compressor is turned off due to a drop in refrigerant pressure, the power relay is turned off in conjunction with the operation of the low-pressure switch, thus shutting off the supply of power to the indoor unit. Accordingly, the air conditioner cannot perform a heating operation using the electric heater 9. That is, since a cooling operation is not performed while an outdoor air temperature is low, as in the winter, it is desirable that the low-pressure switch is not operated. However, since the low-pressure switch is turned off due to a drop in refrigerant pressure caused by a low outdoor air temperature, it is almost impossible to perform a heating operation using an electric heater.

SUMMARY OF THE INVENTION

[0011] Accordingly, it is an object of the present invention to provide an air conditioner and method of controlling the same which is capable of supplying power to an indoor unit to allow a heating operation to be performed using an electric heater even though a low-pressure switch is turned off due to a drop in refrigerant pressure in the coldest season.

[0012] Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

[0013] The foregoing and other objects of the present invention are achieved by providing an air conditioner comprising: a low-pressure switch to shut off the supply of power to an indoor unit when a refrigerant pressure in a suction side of a compressor is decreased; and a power supply unit to supply power to an indoor unit of the air conditioner so that a heating operation is performed using an electric heater mounted in the outdoor unit even though the low-pressure switch is turned off.

[0014] The power supply unit may supply power to the indoor unit if an outdoor air temperature is equal to or lower than a preset reference temperature.

[0015] The power supply unit comprises: a relay connected in parallel to the low-pressure switch; an outdoor air temperature detecting unit to detect an outdoor air temperature; a control unit to output a relay drive signal to turn the relay on if a detected outdoor air temperature is equal to or lower than the preset reference temperature; and a relay drive unit to turn on the relay according to the relay drive signal of the control unit.

[0016] In addition, the present invention provides a method of controlling an air conditioner in which when a refrigerant pressure in a suction side of a compressor is decreased, a low-pressure switch provided in an outdoor unit is turned off to shut off power to an indoor unit, the method comprising: determining whether a current operation mode of the air conditioner is a heating operation mode; supplying power to the indoor unit even though the low-pressure switch is turned off in a heating operation mode; and performing a heating operation mode by operating an electric heater mounted in the indoor unit.

[0017] In an embodiment of the present invention, the supplying of power comprises: detecting an outdoor air temperature in a heating operation mode; determining whether a detected outdoor air temperature is equal to or lower than a reference temperature; and supplying power to the indoor unit by operating a relay connected in parallel to the low-pressure switch when the detected outdoor air temperature is equal to or lower than the reference temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and other objects and advantages of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

[0019]FIG. 1 is a partial cross section of a conventional air conditioner;

[0020]FIG. 2 is a circuit diagram of the conventional air conditioner;

[0021]FIG. 3 is a circuit diagram illustrating an air conditioner in accordance with an embodiment of the present invention; and

[0022]FIG. 4 is a flowchart illustrating the control of an outdoor unit microcomputer of the air conditioner in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.

[0024]FIG. 3 is a circuit diagram of an air conditioner in accordance with an embodiment of the present invention. As illustrated in the drawing, the air conditioner of the present invention comprises a power relay 11 connected to a power line connecting an external power source 10 and an indoor unit, a low-pressure switch 12 connected in series to a coil of the power relay 11, an indoor unit microcomputer 13 mounted in the indoor unit to control the operation of an electric heater 9, and an electric heater drive unit 14 to operate the electric heater 9 under the control of the indoor unit microcomputer 13.

[0025] In addition, the air conditioner of the present invention further comprises a relay 23 connected in parallel to the low-pressure switch 12, a relay drive unit 22 to operate the relay 23, an outdoor air temperature detecting unit 20 to detect an outdoor air temperature, and an outdoor unit microcomputer 21 to output a relay drive signal to the relay drive unit 22 to drive the relay 23.

[0026] The outdoor microcomputer 21 determines whether to operate the relay 23 or not by comparing an outdoor air temperature detected by the outdoor air temperature detecting unit 20 with a preset reference temperature. That is, since the external power source 10 can be disconnected from the indoor unit when the low-pressure switch 12 is likely to be turned off due to a drop in outdoor air temperature, the relay 23 is turned on to prevent such an occurrence. In this case, the reference temperature refers to a temperature at which the refrigerant pressure is reduced due to a low outdoor air temperature to cause the low-pressure switch 10 to be turned off, preferably about −10° C.

[0027] The outdoor unit microcomputer 21 determines whether the operation mode of the air conditioner is a heating operation mode through the indoor unit microcomputer 13 and a communication line (not shown), and controls the operation of the relay 23 according to the outdoor air temperature detected in a heating operation mode.

[0028] The outdoor air temperature detecting unit 20 comprises a thermistor TH and resistors R1 and R2, and outputs a detection signal corresponding to an outdoor air temperature to the outdoor unit microprocessor 21. This occurs because the resistance value of the thermistor TH varies with the outdoor air temperature.

[0029] The relay drive unit 22 comprises a resistor R3 and a transistor TR. The transistor TR is turned on or off according to a relay driving signal outputted from the outdoor unit microcomputer 21. That is, when the detected outdoor air temperature is lower than the reference temperature, the outdoor unit microcomputer 21 outputs a relay driving signal to the relay drive unit 22. As a result, the transistor TR is turned on, so a driving power of +12V is supplied to the coil of the relay 23, thereby turning the contact of the relay 23 on. Meanwhile, when the outdoor unit microcomputer 21 outputs a relay driving signal to turn the relay 23 off, the transistor TR is turned off. Accordingly, the driving power of +12V is not supplied to the coil of the relay 23, so the contact of the relay 23 is turned off.

[0030] The low-pressure switch 12 is mounted in the suction side of the compressor, and is turned off when refrigerant pressure is decreased to a level equal to or lower than a reference pressure. In this case, the outdoor microcomputer 21 turns the relay 23 on, so the external power source 10 is not disconnected from the indoor unit, but is applied to the indoor unit. Accordingly, the indoor unit microcomputer 13 outputs a heater driving signal to the electric heater drive unit 14 to perform a heating operation set by a user, thereby operating the electric heater 9.

[0031] That is, if the relay 23 is turned on even though the low-pressure switch 12 is turned off, the driving power of +12V is supplied to the coil of the power relay 11. As a result, the contact of the power relay 11 is turned on, so the external power source 10 is applied to the indoor unit of the air conditioner.

[0032] The control of the air conditioner of the present invention is described with reference to FIG. 4.

[0033] The outdoor unit microcomputer 21 determines whether the current operation mode of the air conditioner is a heating operation mode while communicating with the indoor unit microcomputer 13 through a communication line at operation S10. The process returns to operate the air conditioner according to a corresponding operation mode if the current operation mode of the air conditioner is not a heating operation mode, while the outdoor unit microcomputer 21 detects an outdoor air temperature using a detection signal inputted through the outdoor temperature detection unit 20 if the current operation mode of the air conditioner is a heating operation mode, at operation S20.

[0034] Thereafter, the outdoor unit microcomputer 21 determines whether the outdoor air temperature is equal to or lower than a preset reference temperature at operation S30. In this case, the reference temperature refers to a temperature at which refrigerant pressure is reduced due to a low outdoor air temperature in the coldest season to cause the low-pressure switch 10 to be turned off.

[0035] If as the result of the determination at operation S30, the detected outdoor air temperature is equal to or lower than the reference temperature, a relay driving signal is outputted to the relay drive unit 22 to turn the relay 23 on. Accordingly, the transistor TR is turned on, so the contact of the relay 23 is turned on at operation S40. As a result, since the power relay 11 is turned on even though the low-pressure switch 12 is turned off, the external power source 10 is applied to the indoor unit of the air conditioner. Thereafter, the indoor unit microcomputer 13 controls the operation of the electric heater 9 so that a heating operation can be performed.

[0036] If as the result of the determination at operation S30, the detected outdoor air temperature is higher than the reference temperature, a relay driving signal is outputted to the relay drive unit 22 to turn the relay 23 off. Accordingly, the transistor TR is turned off, so the contact of the relay 23 is turned off at operation S50.

[0037] As described above, the present invention provides an air conditioner and method of controlling the same, which is capable of operating the power relay connected in series with the low-pressure switch even though the low-pressure switch is turned off due to a drop in refrigerant pressure caused by a low outdoor air temperature, so the external power source can be applied to an indoor unit, thereby performing a heating operation using an electric heater.

[0038] Although a few embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 

What is claimed is:
 1. An air conditioner having an outdoor unit with an electric heater and an indoor unit with a compressor, comprising: a low-pressure switch to shut off supply of power to said indoor unit when a refrigerant pressure in a suction side of said compressor is decreased to a level equal to or below a reference pressure; and a power supply unit to supply power to said indoor unit of the air conditioner to perform a heating operation using said electric heater mounted in said outdoor unit when said low-pressure switch is turned off.
 2. The air conditioner according to claim 1, wherein said power supply unit supplies power to said indoor unit if an outdoor air temperature is equal to or lower than a preset reference temperature.
 3. The air conditioner according to claim 2, wherein said power supply unit comprises: a relay connected in parallel to said low-pressure switch; an outdoor air temperature detecting unit to detect an outdoor air temperature; a control unit to output a relay drive signal to turn said relay on if the detected outdoor air temperature is equal to or lower than said preset reference temperature; and a relay drive unit to turn on said relay according to the relay drive signal of said control unit.
 4. A method of controlling an air conditioner in which when a refrigerant pressure in a suction side of a compressor is decreased, a low-pressure switch provided in an outdoor unit is turned off to shut off power from an indoor unit, comprising: determining whether a current operation mode of the air conditioner is a heating operation mode; supplying power to an indoor unit when a low-pressure switch is turned off in the heating operation mode; and performing the heating operation mode by operating an electric heater mounted in the indoor unit using the supplied power.
 5. The method according to claim 4, wherein said supplying of the power comprises: detecting an outdoor air temperature in the heating operation mode; determining whether the detected outdoor air temperature is equal to or lower than a reference temperature; and supplying the power to the indoor unit by operating a relay connected in parallel to the low-pressure switch when the detected outdoor air temperature is equal to or lower than the reference temperature.
 6. An air conditioner having a compressor and a heating element, comprising: a low-pressure switch terminating flow of power to said heating element upon detection of a predetermined decrease in refrigerant pressure in said compressor; and a power supply unit bypassing said low-pressure switch, to provide the power to said heating element in a heating operation mode.
 7. An air conditioner having predetermined components, comprising: a low-pressure switch terminating flow of power to said predetermined components in response to detection of a decrease in refrigerant pressure in said air conditioner; and a power supply unit bypassing said low-pressure switch, to provide the power to said predetermined components in a corresponding operation mode.
 8. The air conditioner according to claim 7, wherein said power supply unit comprises: a relay connected in parallel to said low-pressure switch; an outdoor air temperature detecting unit to detect an outdoor air temperature; a control unit to output a relay drive signal to turn said relay on if the detected outdoor air temperature is equal to or lower than said preset reference temperature; and a relay drive unit to turn on said relay according to the relay drive signal of said control unit. 